Google Groups File Attachment Restrictions Bypassed via Email Posting
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A significant security vulnerability has been identified in Google Groups, allowing users to circumvent file attachment restrictions by simply sending emails to group addresses.\u00a0<\/p>\n
This broken access control issue potentially impacts thousands of organizations that rely on Google Groups for controlled information sharing and collaboration.<\/p>\n
Ph.Hitachi recently observed the vulnerability, which exploits a disconnect between two Google Groups features: attachment permissions and email posting capabilities.<\/p>\n
According to the technical report, even when group administrators explicitly restrict file upload permissions to \u201cowners only,\u201d regular members can bypass this restriction by sending an email with attachments to the group\u2019s email address.<\/p>\n
The \u201cAllow Email Posting\u201d setting is at the core of this vulnerability. This setting enables members to contribute to discussions by sending emails directly to the group\u2019s address (typically formatted as groupname@googlegroups.com).\u00a0<\/p>\n
While this feature facilitates easier participation, it fails to enforce the attachment restrictions configured in the group\u2019s settings.<\/p>\n
The report notes<\/a> that the attachment should be blocked if the group setting specifies that only owners can add files. It highlights the expected behavior versus the actual outcome, where the attachment is successfully posted despite the restriction.<\/p>\n The reproduction steps for this vulnerability are straightforward:<\/p>\n This vulnerability represents a classic broken access control<\/a> issue where permission checks are inconsistently applied across different access methods to the same resource.<\/p>\n\n